To enter
this posture, begin in crane pose. From a squatting position, place
the hands on the ground shoulder-distance apart. Lift the hips, placing the knees against the upper arms. Carefully shift the weight
to the hands as the feet lift off the ground and the elbows
straighten. From crane pose, extend one leg straight back to complete
one-legged crane pose.

The posture is also known by its Sanskrit name, eka pada bakasana.

Yogapedia explains One-Legged Crane Pose

One-legged crow pose is often used to describe this posture, but when a distinction between the postures is made, the crow pose variations are performed with bent arms while the crane versions are with straight arms.

Because one-legged crane pose is an
advanced posture that requires strength and balance, it should only be attempted after mastering crane pose. Meeting the
challenge of the one-legged variation, though, has its benefits, including stabilization of the nervous system and creating a sense of grounding. The asana strengthens the arms, wrists, back and abdominal muscles while building balance and coordination. It also opens the groin, boosts confidence and encourages mindfulness.

To ease into
the pose, a booster such as a yoga block may be used under the feet.